U.S. Pat. No. 6,443,447 B1, entitled “Method And Device For Moving Cut Sheets in a Sheet Accumulating System” and U.S. Pat. No. 7,752,948 B2, entitled “Method and Apparatus for Enhanced Cutter Throughput Using an Exit Motion Profile”, both address sheet alignment by having a velocity motion profile. A first path's initial speed is greater than an adjacent second path until it is determined that it must be decelerated to the adjacent second path's speed to be delivered to the downstream module at the desired lead edge to lead edge distance/offset.
U.S. Pat. No. 6,764,070 B2, entitled “Path Length Compensation Method and Device for High Speed Sheet Cutters” addresses sheet alignment by increasing the path length at which one document must travel such that the lead edge to lead edge distance/offset is at the desired amount upon entering a Turnover Sequencer (TOS)/Right Angle Turn (RAT).
The existing technology does not address the requirement for positive control of both the left and right sheets' alignment being adjusted in position relative to each other. In addition, existing technology does not account for the initial alignment of the sheets as received from an upstream module.
Current sheet synchronization systems only adjust relative position of the side by side sheets to account for the path length difference that the sheets experience when traveling through the turnover sequencer (TOS). This synchronization is accomplished by using a different velocity motion profile for each sheet. The velocity profile must include an acceleration and deceleration rate that does not cause paper damage or slippage in the sheet drive. The steady state velocity must be maintained between the acceleration and deceleration period such that the total motion profile for each sheet produces the desired overlap of the sheets upon output from the TOS. The total motion profile is a complex command sequence. The total motion profile configuration only accounts for the TOS path length difference and cannot account for the amount of offset between the sheets that results from the cutting and advancement of the sheets out of the cutter.
Hence a need exists for measurement of the sheets initial alignment upon reception from an upstream module and for using separate servo motor position control for both the left and right sheets to employ a sequence of position control adjustments to each sheet during the sheet transition through the hold module.